The Multiple-Input Multiple-Out (MIMO) technology is widely used in wireless communication systems such as the Long Term Evolution (LTE). In the Multi-User MIMO (MU-MIMO) technology, a key processing step is precoding. In the MIMO technology, a base station transmits signals to multiple terminals using a same frequency and a same time slot; and since the multiple terminals cannot corporate with each other, mutual interferences among the multiple terminals are caused and signals received by the terminals are of poor quality. The mutual interferences among the terminals can be reduced through performing a precoding processing at the base station side. Specifically, when performing the precoding processing, the base station needs to obtain a state of a downlink channel and perform the precoding processing using the state of the downlink channel. It should be noted that, if the precoding processing has been performed by the base station, the terminals need to obtain downlink channel response information and perform MIMO detections on received data symbols by using the downlink channel response information, such that the terminals can correctly receive the signals transmitted by the base station. A method for enabling a terminal to obtain the downlink channel response information includes that: mapping a user-specific reference signal to a resource block scheduled by the terminal, by the base station through transmitting the user-specific reference signal to the terminal, such that the terminal obtains the downlink channel response information through channel estimation. The precoding may be classified into linear precoding and nonlinear precoding generally, and the Tomlinson Harashima Precoding (THP) is a typical nonlinear precoding technology. During a process of transmitting the user-specific reference signal, the base station needs to perform an interference elimination processing on the user-specific reference signal, such that the terminal obtains a relative accurate state of the downlink channel. For the linear precoding technology, a same interference elimination processing is performed on the user-specific reference signal and a data signal. However, for the nonlinear precoding technology, the power of the user-specific reference signal may be increased through the interference elimination processing, and a transmitting power for the data signal may be decreased due to a limited transmitting power of the base station, thereby degrading performance of a communication system. In order to control the transmitting power for the user-specific reference signal, a modulus operation needs to be performed to control the power of the user-specific reference signal. However, the user-specific reference signal may have a modulus offset through the modulus operation, and the modulus offset of the user-specific reference signal can not be obtained by the terminal; hence, a relative large error may be caused in the channel estimation performed by the terminal, and the communication system is of poor performance.